US4325635A
Expired / Lapsed
US
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Heterodyne indicial refractometer
Assignee: United States Department of the Army
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Filing: 1980-10-07
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Granted: 1982-04-20
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Expires: 2000-10-07
Abstract
Abstract A method and apparatus for simply and accurately determining the index of refraction of semiconductor materials, etalon bars and materials transparent to infrared radiation. The channel spectra of the material is obtained by passing through it a portion of radiation from a continuously tuned diode laser. Another portion of the diode laser radiation is heterodyned with radiation from a CO 2 laser to obtain heterodyne marker beats. The channel spectra and marker beats are displayed in conjunction whereby the frequency difference between the marker beats can be related to the number of fringes in the channel spectra between the marker beats.
Inventors
- 👤 Joseph P. Sattler
- 👤 Terrance L. Worchesky
- 👤 Kenneth J. Ritter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:50
CPC Classifications
G; G01; G01N; G01N21/00; G01N21/17; G01N21/41; G01N21/45
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
102 words
A method of measuring the index of refraction of a material which comprises the steps of: obtaining a first beam of radiation by continuously tuning a first source of radiation through a selected range of frequencies; determining the channel spectra of the material by directing a portion of the first beam of radiation through a known length of the material; obtaining heterodyne marker beats by heterodyning a portion of the first beam of radiation with a second beam of radiation from a second source of radiation; and determining the index of refraction by comparing the channel spectra to the heterodyne marker beats.
Claim 2
Independent Claim
102 words
A method of measuring the index of refraction of a material which comprises the steps of: obtaining a first beam of radiation by continuously tuning a first source of radiation through a selected range of frequencies; determining the channel spectra of the material by directing a portion of the first beam of radiation through a known length of the material; obtaining heterodyne marker beats by heterodyning a portion of the first beam of radiation with a second beam of radiation from a second source of radiation; and determining the index of refraction by comparing the channel spectra to the heterodyne marker beats.
Claim 3
Dependent Claim
63 words
A method of measuring the index of refraction of a material as recited in claim 1 wherein the step of obtaining heterodyne marker beats is accomplished by: mixing a portion of the first beam of radiation with the second beam of radiation; selecting upper and lower heterodyne beats to be used as the marker beats; and detecting and displaying the selected marker beats.
Claim 4
Dependent Claim
48 words
A method of measuring the index of refraction of a material as recited in claim 2, wherein the step of determining the channel spectra of the material is accomplished by: detecting the channel spectra signal; and displaying the channel spectra signal in conjunction with the selected marker beats.
Claim 5
Dependent Claim
56 words
A method of measuring the index of refraction of a material as recited in claim 3, wherein the step of determining the index of refraction is accomplished by: determining the number of fringes in the channel spectra signal between the marker beats; and relating the number of fringes to the frequency difference between the marker beats.
Claim 6
Dependent Claim
35 words
A method of measuring the index of refraction of a material as recited in claim 4, wherein the first beam of radiation is obtained by injecting a current of varying amplitude into a diode laser.
Claim 7
Dependent Claim
29 words
A method of measuring the index of refraction of a material as recited in claim 5, wherein the second beam of radiation is obtained from a fixed frequency laser.
Claim 8
Independent Claim
92 words
An apparatus to measure the index of refraction of a material comprising: means, continuously tunable through a selected range of frequencies, for obtaining a first beam of radiation; means for dividing said first beam of radiation into portions and for directing one portion of said first beam of radiation through a known length of the material; means for determining the channel spectra of the material; means for obtaining a second beam of radiation; means for producing heterodyne marker beats; and comparing means for comparing said channel spectra with said heterodyne marker beats.
Claim 9
Independent Claim
92 words
An apparatus to measure the index of refraction of a material comprising: means, continuously tunable through a selected range of frequencies, for obtaining a first beam of radiation; means for dividing said first beam of radiation into portions and for directing one portion of said first beam of radiation through a known length of the material; means for determining the channel spectra of the material; means for obtaining a second beam of radiation; means for producing heterodyne marker beats; and comparing means for comparing said channel spectra with said heterodyne marker beats.
Claim 10
Dependent Claim
67 words
An apparatus to measure the index of refraction of a material as recited in claim 7 wherein the means for producing heterodyne marker beats comprises: a photomixer, wherein a second portion of said first beam of radiation is mixed with said second beam of radiation; and a selection means for selecting the locations of upper and lower marker beats; and a means for detecting said marker beats.
Claim 11
Dependent Claim
36 words
An apparatus to measure the index of refraction of a material as recited in claim 8 wherein the means for determining the channel spectra of the material comprises a detector to detect the channel spectra signal.
Claim 12
Dependent Claim
53 words
An apparatus to measure the index of refraction of a material as recited in claim 9 wherein the comparing means comprises a visual display of said channel spectra signal and said marker beats wherein the number of fringes in said channel spectra signal is related to the frequency difference between said marker beats.
Claim 13
Dependent Claim
30 words
An apparatus to measure the index of refraction of a material as recited in claim 10 wherein the means for obtaining a first beam of radiation comprises a diode laser.
Claim 14
Dependent Claim
31 words
An apparatus to measure the index of refraction of a material is recited in claim 11 wherein the means for obtaining a second beam of radiation comprises a fixed frequency laser.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1985-04-19 | 1985-10-19 | 1986-04-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-04-19 | 1989-10-19 | 1990-04-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-04-19 | 1993-10-19 | 1994-04-20 | $7700.00 | Window Closed / Lapsed |